I have a new 600 cfm 1406 Edelbrock on my newly rebuilt 273. It has a D4B hi-rise, stock .030 over flat pistons, an electronic ignition and mild cam ( duration 240/240, .050 duration 212/212, lift .290, valve lift .435/.435, centerline .106/.114, lobe separation 110). My idle vacuum is 18" at...